In recent times an electronically controlled sewing machine has been introduced into the marketplace and is generally of the type illustrated in U.S. Pat. No. 3,872,808, issued Mar. 25, 1975. In such a machine a static read-only-memory device is provided in which is stored stitch pattern coordinates for the needle positions and fabric feed positions for a selected number of stitch patterns. Upon selection of a pattern from a pattern display on a machine, the read-only-memory is addressed and information is released in accordance with timing pulses coordinated with the mechanism of the machine which signals are converted from digital to analogue form and fed to an actuating mechanism for the needle position and the fabric feed position to reproduce the selected pattern. With such machines the number of patterns that can be selected is restricted in accordance with the capacity of the read-only-memory device and once the patterns are fed into such a memory they are locked therein. In other words, the machine does not possess the capability of reprogramming or selective programming by operator generated information.
Dynamic programming devices such as tape drives of the magnetic and punched varieties, for example, are not practical for use in sewing machines since they require relatively elaborate power supplies for their operation. Also, tape-type memories must be recorded and read sequentially, and therefore, the operator cannot select patterns at random or from different sections of the memory at will. One such device applied to a sewing machine is illustrated in Japanese Patent Publication No. 15713/70 published on June 1, 1970. However, the machine disclosed in the Japanese patent only purports to provide needle control for production of geometric patterns and is not capable of producing non-geometric patterns which require both signals for the needle and the fabric feed. Further, a machine of this type has never been successfully introduced into the market place.
One solution to the problem of providing a re-programmable memory for a sewing machine has been proposed and disclosed in U.S. Patent application Ser. No. 631,776, filed Nov. 13, 1975 by Herr et al. and assigned to the same assignee as the present application. In this referenced application, a magnetizable material is utilized for the memory which can be selectively magnetized by the operator in accordance with pattern instructions. The magnetizable memory is then read by the machine to reproduce the pattern either by mechanical means or electronic means.